Originally Posted by LukasM
Looks like you read many of the same forums as I did a few months ago, that is where my recommendation for the Compufire regulator comes from.
I am pretty sure the whole "generator" assembly (stator + flywheel) is indeed made by Denso (as for most other bikes), so the problem is probably unrelated to Rotax.
I can tell ya it took me hours and I had a massive headache as I also tried to look through some literature explaining what is going on inside an alternator, especially the part with the regulators. There is also a British (?) Aprilia forum where you can find 30 pages of discussion about exactly the same issue. Some guys really postet something like a doctoral research study. Similar with Triumphs and Buells.